When most people get their DEXA results, they look for one number, the T-score, and try to figure out whether it puts them in the osteopenia or osteoporosis range. If your report stopped there a few years ago, that was reasonable. Today, many modern DEXA reports include two additional pieces of information that can meaningfully change a treatment decision: Trabecular Bone Score (TBS) and Vertebral Fracture Assessment (VFA). They look like extras, but in the right patient they are not extras at all. They are the parts of the report that sometimes flip the answer.
I want to walk you through what each one is, when it matters, and what to ask your doctor if your report includes them.
A Quick Refresher on the T-Score
Your T-score compares the amount of mineral in your bone to a healthy young adult reference. It is a measure of quantity. What it cannot tell you is whether the bone you have is well organized internally, or whether you have already had a small vertebral fracture that you did not feel. Two people with identical T-scores can have very different real-world fracture risk, and the rest of the DEXA report is where that difference shows up.
What Is Trabecular Bone Score (TBS)?
Trabecular Bone Score is a measurement of bone quality, derived from the same lumbar spine images that produce your spine T-score. The software analyzes the subtle gray-scale variations in the image to estimate how well organized the inner, sponge-like (trabecular) bone is. A more uniform, finely textured pattern produces a higher TBS. A coarser pattern, where the internal struts have thinned and disconnected, produces a lower TBS (PMC review of TBS clinical performance, 2025).
TBS is usually reported as one of three categories:
- Normal: TBS above about 1.31
- Partially degraded: TBS roughly 1.23 to 1.31
- Degraded: TBS below about 1.23
The key point is that TBS predicts fractures independently of your T-score. Someone in the osteopenia range with a degraded TBS can have a higher real-world fracture risk than someone formally in the osteoporosis range with a normal TBS. That is not a paradox. It is what happens when you measure two different aspects of bone instead of one.
How TBS Changes a Treatment Decision
The 2023 International Society for Clinical Densitometry positions are explicit: TBS is appropriate for adults 40 and older, and it is most likely to change clinical management when you are close to a treatment threshold (ISCD 2023 Official Positions). In practice this means TBS most often helps in three situations:
- You are in the osteopenia range and your FRAX risk is close to the line where treatment is recommended.
- You have a condition known to weaken bone quality more than bone density, such as type 2 diabetes, primary hyperparathyroidism, chronic kidney disease, rheumatoid arthritis, or long-term glucocorticoid use (ABC of TBS, OFNM).
- Your spine T-score is artificially inflated by arthritis or calcifications and you want a measure of spine bone that those changes do not contaminate.
When TBS is added to FRAX as an adjustment, your ten-year fracture probability can shift up or down enough to change whether a medication is offered (ISCD 2023 TBS position, ScienceDirect). The TBS adjustment is available both on the standard FRAX website and through the newer FRAXplus tool, which combines TBS with other adjustments such as recent falls, glucocorticoid dose, and type 2 diabetes (FRAXplus adjustments overview, 2023). FRAXplus is still relatively new, and not every doctor has used it yet, so it is reasonable to mention it by name. I have written a full guide to what FRAX measures, how to run it yourself, and when FRAXplus is worth asking for in Your FRAX Score. If your DEXA report includes a TBS value but not a TBS-adjusted FRAX, that is a fair thing to ask for.
What Is Vertebral Fracture Assessment (VFA)?
Vertebral Fracture Assessment is a side-view image of your spine taken on the DEXA machine at the time of your scan. It is a low-radiation way to look directly at the vertebrae and check for fractures that have already happened, often silently.
This matters more than it sounds. Most vertebral fractures are not diagnosed when they occur. Estimates from population studies suggest that roughly two-thirds of vertebral compression fractures go undetected, because the back pain is mild, or attributed to a strain, or there is no pain at all (Vertebral fracture epidemiology and DXA-based VFA, PMC). And yet a single vertebral fracture, even a small wedge nobody noticed, is one of the strongest predictors that another fracture is coming.
The 2023 ISCD guidelines recommend VFA when the T-score is below -1.0 plus at least one of the following risk factors (Age and Ageing summary of ISCD VFA criteria, 2024):
- Women age 70 or older, or men age 80 or older
- Historical height loss of more than 4 cm (about 1.5 inches) from peak
- A self-reported but undocumented prior vertebral fracture
- Regular use of oral glucocorticoids
If a VFA shows even one previously unrecognized vertebral fracture, your diagnosis moves to established osteoporosis regardless of T-score, and that almost always triggers a recommendation for pharmacologic treatment.
How These Tools Fit Together
Think of your DEXA report as answering three different questions about your bones.
- T-score asks: how much bone do I have?
- TBS asks: how well organized is the bone I have?
- VFA asks: has my spine already shown signs of damage?
You can have a reassuring answer to one of those and a worrying answer to another, and the worrying one is often what should drive the plan. A patient with osteopenia by T-score, a degraded TBS, and a small wedge fracture on VFA is not a "borderline" case. That is high-risk osteoporosis hiding in plain sight, and the treatment conversation should look very different than it would based on the T-score alone.
Radiation, Time, and Cost: The Practical Questions
Whenever I write about adding something to a scan, the same three questions come back, and they deserve straight answers.
Does TBS add radiation?
No. TBS isn't a picture. It's software that reanalyzes the lumbar spine image your scanner already captured, so there's no extra scan, no extra exposure, and nothing different for you to do on the table. The added work happens after you've gone home, on the technologist's and the reading doctor's side.
Does VFA add radiation?
A little, because it's a genuine extra image. But the amount is strikingly small. A VFA delivers a tiny fraction of the dose of a single conventional lateral spine X-ray, on the order of one percent or less, which lands it somewhere in the neighborhood of a day or two of the ordinary background radiation you'd absorb just living your life (VFA versus spine radiography cost-effectiveness analysis, BMC Musculoskeletal Disorders). That difference is the whole reason VFA exists as an alternative to sending you out for spine films.
Does either one add time?
Barely. The VFA image itself takes seconds, and TBS adds nothing at all to your time on the table. What both add is interpretation time on the back end, which is one quiet reason not every center offers them.
Are they on every DEXA scanner?
No, and this is the part that frustrates patients most. TBS is an add-on software module for Hologic and GE Lunar systems, so whether your report includes it depends entirely on whether your imaging center bought and installed it (Illinois Bone & Joint Institute). VFA requires a scanner with lateral imaging capability and a technologist trained to capture and a doctor willing to read it. Availability varies a great deal by region and by whether the center is oriented toward bone health specifically.
Do they cost extra?
Often yes, though usually modestly. TBS isn't billed as a separate test. It's an additional component of the DEXA, billed under its own codes, and it is frequently covered when the DEXA itself is indicated, including under Medicare (Illinois Bone & Joint Institute). VFA is billed separately too, and in cost-effectiveness studies it consistently comes out cheaper than sending someone for conventional spine radiographs (BMC Musculoskeletal Disorders). Coverage still varies by plan, so if cost matters to you, call ahead and ask what the center charges and what your plan does with those codes. That's a reasonable question, and the scheduling staff hear it often.
One more limitation worth knowing about TBS: it can only be calculated when the lumbar spine can be measured cleanly. Extensive spinal hardware from prior surgery can make it impossible, and the score has only been validated in a body mass index range of roughly 15 to 37, so it may not be reported at either extreme.
If your report doesn't include TBS or VFA and your situation suggests they'd help, it's fair to ask whether a nearby facility offers them, or whether your existing scan images can be reanalyzed.
What to Ask at Your Next Appointment
- Does my DEXA report include a TBS value, and if so, what is the number and category?
- Was a TBS-adjusted FRAX calculated, and does it change my ten-year fracture risk? Could we run my numbers through FRAXplus to factor in falls, steroid use, or diabetes as well?
- Do I meet the criteria for a VFA, and if so, was one done at my last scan or should one be added next time?
- If I have a known risk factor like diabetes or steroid use, are we factoring bone quality into my plan and not only bone density?
- Have I lost height since my peak adult height, and should that prompt additional imaging?
The reason I keep coming back to these two measures is that they answer the question patients actually care about, which is not "what is my T-score" but "what is my fracture risk, and what should I do about it." T-score is a piece of that answer. TBS and VFA, when they are available, often turn out to be the piece that decides.